Minimum clearance

What's the minimum clearance for threaded 1.5in sch 80 bulkhead behind the tank with a street 90 ?

 

is that a bulkhead coming from the bottom of a drilled tank or bulkhead on the bottom of an HOB overflow?

 

i think 3" but I am not sure... but double check on that first

 

If you include the back side of the bulkhead plus the elbow, it may be close to 4". Here is a link to SCH 80 fitting dimensions. Elbows start on page 15 and bulkheads page 80.

http://www.spearsmfg.com/prod_dimensions_spec/80-4-0411_0411_web.pdf

 

I'm drilling the back of a tank. I have 4.5 inches I think ill b good. Thanks guys